Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của flashmt

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

int n, Q, id[256], flag[256], cnt[55][55];
char s[1000100], t[100];

int main()
{
    for (char c = 'a'; c <= 'z'; c++) id[c] = c - 'a';
    for (char c = 'A'; c <= 'Z'; c++) id[c] = c - 'A' + 26;

    scanf("%d%s", &n, s);
    for (int i = 1; i < n; i++) 
    {
        int x = id[s[i - 1]], y = id[s[i]];
        if (x > y) swap(x, y);
        cnt[x][y]++;
    }

    scanf("%d", &Q);
    for (int iq = 1; iq <= Q; iq++)
    {
        scanf("%s", t);
        int len = strlen(t);
        for (int i = 0; i < len; i++) flag[id[t[i]]] = iq;

        int ans = 0;
        for (int i = 0; i < 52; i++)
            for (int j = i + 1; j < 52; j++)
                if ((flag[i] == iq) ^ (flag[j] == iq))
                    ans += cnt[i][j];

        if (flag[id[s[0]]] == iq) ans = ans / 2 + 1;
        else ans = (ans + 1) / 2;
        printf("%d\n", ans);
    }
}

Code mẫu của ladpro98

program VMSUBSTR;
uses    math;
const   fi='';
var     n,qq,t,i,res:longint;
        a,s:ansistring;
        p,q:char;
        chk:array['A'..'z'] of boolean;
        c:array['A'..'z','A'..'z'] of longint;
        inp:text;

begin
        assign(inp,fi);reset(inp);
        readln(inp,n);readln(inp,a);
        for i:=2 to n do
        begin
                inc(c[a[i],a[i-1]]);
                inc(c[a[i-1],a[i]]);
        end;
        readln(inp,qq);
        for t:=1 to qq do
        begin
                readln(inp,s);
                res:=0;
                for i:=1 to length(s) do chk[s[i]]:=true;
                if chk[a[1]] then inc(res);
                if chk[a[length(a)]] then inc(res);
                for p:='A' to 'z' do
                for q:=chr(ord(p)+1) to 'z' do
                if chk[p]<>chk[q] then inc(res,c[p,q]);
                writeln(res shr 1);
                for i:=1 to length(s) do chk[s[i]]:=false;
        end;
end.

Code mẫu của RR

// Author: RR. Expected point: 100
#include <sstream>
#include <iomanip>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <string>
#include <deque>
#include <complex>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define FORN(i,a,b) for(int i=(a),_b=(b);i<_b;i++)
#define DOWN(i,a,b) for(int i=a,_b=(b);i>=_b;i--)
#define SET(a,v) memset(a,v,sizeof(a))
#define sqr(x) ((x)*(x))
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair

#define DEBUG(x) cout << #x << " = "; cout << x << endl;
#define PR(a,n) cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl;
#define PR0(a,n) cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl;
using namespace std;

//Buffer reading
int INP,AM,REACHEOF;
const int BUFSIZE = (1<<12) + 17;
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp && !REACHEOF) { \
        memset(BUF,0,sizeof BUF);\
        int inpzzz = fread(BUF,1,BUFSIZE,stdin);\
        if (inpzzz != BUFSIZE) REACHEOF = true;\
        inp=BUF; \
    } \
    INP=*inp++; \
}
#define DIG(a) (((a)>='0')&&((a)<='9'))
#define GN(j) { \
    AM=0;\
    GETCHAR(INP); while(!DIG(INP) && INP!='-') GETCHAR(INP);\
    if (INP=='-') {AM=1;GETCHAR(INP);} \
    j=INP-'0'; GETCHAR(INP); \
    while(DIG(INP)){j=10*j+(INP-'0');GETCHAR(INP);} \
    if (AM) j=-j;\
}
//End of buffer reading

const long double PI = acos((long double) -1.0);
const int MN = 1000111;

int l, q;
char s[MN], a[55];
bool good[55];
int cnt[55][55];

int getVal(char c) {
    if (c >= 'a' && c <= 'z') return c - 'a';
    else return c - 'A' + 26;
}

void init() {
    REP(i,l-1) {
        int u = getVal(s[i]), v = getVal(s[i+1]);
        cnt[u][v]++;
    }
}

int main() {
    scanf("%d\n", &l);
    gets(s);
    init();
    scanf("%d\n", &q);
    while (q--) {
        gets(a);
        memset(good, false, sizeof good);
        REP(i,strlen(a)) good[getVal(a[i])] = true;

        int res = 0;
        REP(x,52) if (good[x])
        REP(y,52) if (!good[y])
            res += cnt[x][y];

        if (good[getVal(s[l-1])]) ++res;
        printf("%d\n", res);
    }
    return 0;
}